The present invention relates to mechanical fasteners, particularly those used to maintain computer components and modules in physical contact.
In modern computer systems, typically there are components which must be fastened together for proper operation. These may range in size, from tens or hundreds of grams to many kilograms. Screws are commonly used to fasten such components to the main structure, or frame, of the computer. In large systems, there are generally many components, and they can be very massive, sometimes exceeding thirty kilograms.
The use of screws as fasteners presents several problems. The labor involved in aligning and inserting all the screws in a large and complex system can add a significant cost to the assembly of the system, and to the difficulty of servicing the system. With the use of screws, once a component is fixed in place, it remains inflexible. If the contacts on the component and the main structure are not perfectly aligned, damage may result.
Large computer systems, employing multiple subsystems or modules are commonly subject to mechanical or thermal expansion. Further, the presence of liquid coolant lines and manifolds can cause shifting as lines are pressurized. As a result, structural stress is a significant concern. Assembling a system without fully tightening screws until the stresses are equalized and then performing a final tightening is problematic, because it requires additional time on the part of the assembly technician to return and retighten each screw, it also requires extra vigilance, since it may not be possible by visual inspection alone to determine whether a screw is tight. Loose screws may eventually drop out due to varying tension or vibration, causing catastrophic failures in expensive systems. Furthermore, some stresses cannot be equalized or are recurrent as the system cycles.
A further problem is that specialized tools are required to engage screws or other fasteners, and to ensure the correct amount of torque when fastened.
According to the principles of the present invention a fastener is provided that can be engaged and disengaged quickly and easily. The fastener holds components in their proper position firmly, while allowing some limited movement after assembly. The fastener is used to retain a circuit board module within a frame during operation of a computer system.
The fastener has two main components: a body and a head. The body is in the form of a spring, using tightly coiled steel wire. The head is in the form of a knob or nut affixed to one end of the body. The other end of the body is attached to the frame of the system. The module is provided with a slotted flange in a position that corresponds to the location of the fastener, such that, when the module is correctly positioned in the frame, the fastener is in proper alignment with the slot in the flange.
With the structures positioned correctly, the fastener is flexed in a direction perpendicular to the longitudinal axis of the fastener, and then released, such that it engages the slot with the head.
The spring characteristics of the fastener permit some limited movement between the two structures, while the tensile strength of the spring holds the module in the proper position within the frame.